850 



SCIENCE. 



[N. S. Vol. XI. No. 283. 



successfully except a miscliievous "urcliin 

 who had beeu thrashed for saying lohat, and 

 his answer was, ' Give me that stick and 

 I'll what you.' 



Ebasmxis Daewin Preston. 

 ( To be continued. ) 



SANDSTONE DISINTEGBA TION THRO UGH THE 

 FORMATION OF INTERSTITIAL GYPSU3L 



A BLOCK of Carboniferous sandstone from 

 New Brunswick, carved in the form, and in 

 imitation, of the Old Liberty Bell, was 

 some years ago, owing to the crowded con- 

 dition of the Exhibition Halls of the Na- 

 tional Museum in Washington, removed to 

 a point near the northwest entrance, out- 

 side of the building. 



When placed in position the stone was 

 fresh, and surface smooth throughout. 

 Within the space of a couple of years there 

 appeared on the northwest side a slight 

 roughening of the surface and a whitish 

 efflorescence which during the two ensuing 

 years extended gradually two-thirds around 

 the northern and southern sides, but was 

 most marked on the northwest. 



On examination the efflorescence was found 

 to be due to the formation of small gypsum 

 crystals, and the roughening of the surface 

 to the falling away of the siliceous granules. 

 The process has gone on until now more 

 than an eighth of an inch in thickness of 

 material has been removed from the point 

 of surface first attacked, and the inscrip- 

 tion in part obliterated, as shown in the 

 accompanying illustration. It is to be 

 noted that the zone of disintegration is 

 limited wholly to that portion of the bell 

 just above the middle, where the surfaces 

 stand nearly vertical, while elsewhere the 

 material is almost as fresh and unaltered 

 as when first exposed. 



An examination of the stone shows it 

 to contain numerous small segregations of 

 marcasite which are quite inconspicuous, 

 or show up as small dark spots on the 

 weathered surface. Chips of the fresh rock 

 efifervesce slightly in dilute acid, indicating 

 the presence of calcite. The disintegration 

 is doubtless due, therefore to the oxidation 

 of the marcasite through the downward 

 percolation of rain water, and the reaction 

 of the sulphuric acid formed upon the cal- 

 cium carbonate. The resultant calcium 

 sulphate is then brought to near the surface 

 by capillarity where it crystallizes, and, as 

 growth takes place always from the base of 

 the crystals the sand granules are gradually 

 forced ofif in the manner so often exempli- 

 fied in the lifting of soil through the forma- 

 tion of hoar frost. The writer has described 

 (Proc. U. S. Nat. Mus., Vol. XVII., 1894, 

 p. 80) the splitting of blocks of limestone 

 through similar gypsum growths, as noted 

 in the dry portions of Wyandotte and 

 Mammoth Caves, but has never seen the 

 phenomenon so well illustrated in sandstone 

 as here. In as much as it offers an expla- 

 nation for the disintegration of sandstone of 

 this type where exposed in the walls of 

 buildings, the case is worthy of mention. 

 The gypsum efflorescences, it should be 



